Snowmobile planetary drive system

ABSTRACT

Disclosed is a snowmobile including a reduction drive system including planetary gears. In an alternate embodiment, a reversing unit is provided. In a further alternate embodiment, an offset is provided in the drive system.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation in part of U.S. patentapplication Ser. No. 09/843,587 that was filed with the United StatesPatent and Trademark Office on Apr. 26, 2001 that is a continuation inpart of U.S. patent application Ser. No. 09/520,101 that was filed withthe United States Patent and Trademark Office on Mar. 7, 2000. Theentire disclosures of U.S. patent application Ser. Nos. 09/843,587 and09/520,101 are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to snowmobiles and moreparticularly to drive systems for snowmobiles. More particularly, thepresent invention relates to snowmobiles including various embodimentsof drive systems utilizing planetary gears.

BACKGROUND OF THE INVENTION

[0003] Snowmobiles have been known for many years. Early snowmobileswere developed with an appearance that is very primitive compared to thesnowmobile of today. The snowmobile of modern times is a sophisticatedvehicle with heated handle bars, twin head lights, high powered enginesand many other improvements not found in the original snowmobiles.

[0004] One of the weak points in snowmobiles has been the drive system.Snowmobile drive systems have generally included a chain rpm reductiondrive. The rpm of the engine must be reduced prior to applying therotational drive to the differential sprockets driving the track. In thepast the drive system has included a chain and sprocket system. Thechain and sprocket system tends to wear and is subject to extreme abusein the activities of normal snowmobile use. The rapid starts and stops,the very high rpm torque when the snowmobile leaves the ground and leapsinto the air results in extremely rapid changes of speed and load.

[0005] It is also sometimes desired to include in the drive system areverse unit for propelling the snowmobile in reverse direction underpower of the engine. Reverse units of snowmobiles to date have achievedonly low to moderate effectiveness.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 shows a snowmobile of the present invention;

[0007]FIG. 2 shows a perspective view of the snowmobile engine and drivesystem of the present invention;

[0008]FIG. 3 shows a plan view of a chassis including an engine, clutchsystem and the planetary drive system of the present invention;

[0009]FIG. 4 shows a sectional view of the planetary drive system of thepresent invention;

[0010]FIG. 5 shows an exploded view of the planetary drive system of thepresent invention;

[0011]FIG. 6 shows an alternative embodiment of the present snowmobile;

[0012]FIG. 7 shows a plan view of a chassis of an alternative embodimentof the present invention including an engine and the reduced rpm clutchsystem;

[0013]FIG. 8 shows a sectional view of the planetary gear reductionsystem of an alternative embodiment of the present invention;

[0014]FIG. 9 shows an exploded perspective view of a prior art drivetrain;

[0015]FIG. 10 shows an exploded perspective view of a portion of theprior art drive train;

[0016]FIG. 11 shows an exploded perspective view of the parts of a priorart drive train that are eliminated by one embodiment of the presentinvention;

[0017]FIG. 12 is a perspective view of a engine and drive trainaccording to an alternative embodiment of the present invention;

[0018]FIG. 13 is a portion of an alternative embodiment of a portion ofdrive train of the present invention;

[0019]FIG. 14 is an exploded view of a further alternative embodiment ofa planetary gear system of the present invention; and

[0020]FIG. 15 is a sectional view of the planetary gear system shown inFIGS. 12, 13 and 14.

[0021]FIG. 16 is a sectional view of an alternative embodiment planetarygear system including a reverse unit shown in forward mode.

[0022]FIG. 17 is a sectional view of an alternative embodiment planetarygear system including a reverse unit shown in reverse mode.

[0023]FIG. 18 is a sectional view of an alternative embodiment offset incombination with a planetary gear system including a reverse unit.

[0024]FIG. 19 is a sectional view of an alternative embodiment offset incombination with a planetary gear system.

DETAILED DISCLOSURE

[0025] FIGS. 1-8 are the original figures from the parent applicationSer. No. 09/520,101 that was filed with the United States Patent andTrademark Office on Mar. 7,2000. Some changes have been made to FIGS.1-8 for clarification purposes. FIGS. 9-15 are the figures added in theparent application Ser. No. 09/843,587 that was filed with the UnitedStates Patent and Trademark Office on Apr. 26, 2001.

[0026] The snowmobile 10 of the present invention (FIG. 1-5) includes apair of skis 12, which support the forward portion 13 of the snowmobile10. A continuous track 14 supports the rear portion 16 of the snowmobile10. The snowmobile 10 has an engine 17 which is disposed in the forwardportion 13.

[0027] The engine 17 rotatably drives a train 18 which in turns drivesthe endless track 14. The drive train 18 includes an engine drive shaft15, primary clutch 18 a, a drive belt 18 b, a secondary clutch 18 c anda reduction drive 19. The reduction drive 19 may include a drive shaft21 that is rotatably driven by the secondary clutch 18 c. The driveshaft 21 (FIGS. 4 & 5) carries a sun gear 22, which is integral withsaid shaft 21. Note that a “sun gear” is any gear that drives aplurality of planetary gears. Also note, that the “longitudinal axis” ofa shaft is the axis along the length of such shaft. The shaft 21 isrotatably supported in suitable bearings or bushings. Such bearings orbushings may be roller bearings. The embodiment shown in the figuresdepicts the use of single row ball bearings 23 and 24.

[0028] The reduction drive 19 further includes a plurality of planetarygears 26, 27, 28, and 29. The reduction drive 19 is shown having fourplanetary gears 26-29, however, the reduction drive may have any desirednumber of such gears, e.g., three. The planetary gears 26-29 aresupported between a pair of planetary gear plates 31, 32. The plates 31,32 carry a plurality of shafts 36, 37, 38 and 39 which rotatably supportthe gears 26-29 respectively. The shafts 36-39 may be integrally securedto the plates 31, 32, which in turn serve to maintain said gears 26-29in spaced relationship around the sun gear. Spacers 30 may retain plates31, 32 in proper spaced relationship. The shafts 36-39 are secured inthe openings 36 a-39 a, respectively.

[0029] The reduction drive 19 includes a second shaft 43 which isintegral with the plates 31, 32. In other words shaft 43 is locked by akey in the hub 31 a.

[0030] The reduction drive 19 has a housing 40 including first housingmember 41 and a second housing member 42. A ring gear 44 is integrallymounted in the second housing member 41. The ring gear 44 engages theplanetary gears 26-29. The second shaft 43 is integral, e.g., in lockeddriving engagement, with the plates 31, 32 and is driven by planetarygears 26-29. The second shaft 43 serves to drive the endless track 14through sprocket 51.

[0031] The sun gear 22, planetary gears 26-29 and ring gear 44 arecontained in housing 40 including first housing member 41 and secondhousing member 42. The housing members 41 and 42 may be held together bysuitable screws 45.

[0032] The operation of the present invention is apparent from thedescription of the snowmobile 10, however in order to provide a morecomplete understanding of the present invention the operation will befurther described. The engine 17 may be a conventional gasoline poweredengine of the type generally found in snowmobiles. However, the engine17 may be any other type of engine suitable for driving a snowmobile.The engine 17 rotatably drives the primary clutch 18 a which in turndrives the belt 18 b. The drive belt 18 b may drive the secondary clutch18 c which rotatably drives the shaft 21. The sun gear 22 is then drivenby the shaft 21. The sun gear 22 engages the planetary gears 26-29 whichare rotatably supported in the plates 31, 32. The force of the sun gear22 acting on the planetary gears 26-29 cause the gears 26-29 to rotateand move along the ring gear 44 thereby rotating the plates 31, 32. Therotation of plates 31, 32 rotatably drives the second shaft 43. Thesecond shaft 43 rotates at an rpm lower than the rotation of the firstshaft 21 resulting in a gear reduction. The second shaft 43 in turndrives a sprocket 51 acting on the endless track 14, thereby drivingsuch track.

[0033] An Alternative Embodiment of the Present Invention:

[0034] A further embodiment of the present invention snowmobile 110(FIG. 6-8) includes a pair of skis 112 which support the forward portion113 of the snowmobile 110. A continuous track 114 supports the rearportion 116 of the snowmobile 110. The snowmobile 110 has an engine 117which is disposed in the forward portion 113.

[0035] The engine 117 rotatably drives a power train 118 which in turnsdrives the endless track 114. The drive train 118 includes a planetaryreduction gear system 119, which in turn drives a primary clutch 121, adrive belt 122, and a secondary clutch 123. The planetary reductiondrive system 119 may be mounted on the drive shaft 124 of the engine117. The planetary reduction drive system 119 may be similar instructure to planetary reduction drive system 19 shown in FIGS. 4 and 5.The planetary reduction drive system 119 is rotatably driven by theengine drive shaft 124. The engine drive shaft 124 (FIGS. 7 & 8) drivesa drive shaft 127 (also may be referred to as an input shaft) thatcarries a sun gear 126 that is integral with the engine drive shaft 124.The engine drive shaft 124 may be rotatably supported in suitablebearings or bushings. Such bearings or bushings may be roller bearings.The embodiment shown in the figures depicts the use of single row ballbearing 125.

[0036] The reduction drive system 119 further includes a plurality ofplanetary gears 131. The planetary gears 131 are supported between apair of planetary gear plates 136, 137. The plates 136, 137 carry aplurality of shafts 141 which rotatably support the gears 131respectively. The shafts 141 may be integrally secured to the plates136, 137, which in turn serve to maintain said gears 131-134 in spacedrelationship around the sun gear 126. A plurality of spacers 138 mayretain plates 136, 137 in proper spaced relationship such that theplanetary gears 131 may freely rotate there between. The spacers 138 maybe integral with respect to plates 136, 137.

[0037] The reduction drive 119 includes a second shaft 145 which isintegral with respect to the plates 136, 137. Second shaft 145 istapered to fit the primary clutch 121. Of course any shape second shaftthat is capable of driving the primary clutch is within the scope of thepresent invention.

[0038] The reduction drive 119 has a first housing member 151 and asecond housing member 152. A ring gear 154 is integrally mounted in thesecond housing member 152. The ring gear 154 engages the planetary gears131. The second shaft 145 is integral, e.g., in locked drivingengagement, with the plates 136, 137 and is driven by planetary gears131. The second shaft 145 serves to drive the primary clutch 121.

[0039] The sun gear 126, planetary gears 131 and ring gear 154 arecontained in housing 150 including first housing member 151 and secondhousing member 152. The housing members 151 and 152 may be held togetherby suitable screws (not shown).

[0040] The operation of the present invention including the reduced rpmclutch is apparent from the description of the snowmobile 110. Theengine 117 may be a conventional gasoline powered engine. The engine 117has an engine drive shaft 124, which drives a sun gear 126, which inturn drives a plurality of planetary gears 131. The sun gear 126 engagesthe planetary gears 131 which are rotatably supported in the plates 136,137. The force of the sun gear 126 acting on the planetary gears 131cause the gears 131 to rotate and move along the ring gear 154 therebyrotating the plates 136, 137. The rotation of plates 136, 137 rotatablydrives the second shaft 145. The second shaft 145 rotates at an rpmlower than the rotation of the drive shaft 124 resulting in a gearreduction. The second shaft 145 rotatably drives the primary clutch 121which in turn drives the belt 122. The drive belt 122 drives thesecondary clutch 123. Clutch 123 rotatably drives the shaft 157 whichcarries sprocket drives 158 and 159. The sprockets 158, 159 drive thetrack 114.

[0041] Turning now to FIGS. 9-11, a conventional prior art snowmobiledrive system is shown. FIG. 9 is an exploded perspective view of themajor components of a prior art drive system including the engine. FIG.10 is an exploded perspective view of the portion of a prior art drivesystem from the secondary clutch to the track drive sprockets. FIG. 11is an exploded perspective view of the parts of the conventional priorart drive system of FIG. 10 that may be eliminated by one embodiment ofthe present invention.

[0042] The major components of the prior art drive system 270 shown inFIG. 9 are engine 272, primary clutch 274, engine drive shaft (notshown) connecting the engine 272 to the primary clutch 274, drive belt276 (shown in partial cutaway view), secondary clutch 278, driven shaft280, dropcase 282, drive chain 284, top drive sprocket 286, bottom drivesprocket 288, dropcase cover 290, shaft 292 and track drive sprockets294 and 296.

[0043]FIG. 10 includes the major components from the secondary clutch278 to the track drive sprockets 294 and 296 as well as additionalcomponents of the conventional prior art drive train system 270.

[0044] The parts of a chain and sprocket rpm reduction drive of theprior art are subject to wear and tear and tend to require highmaintenance. Furthermore, the use of a chain and sprocket reductiondrive requires that the drive system, including the engine drive shaft,have three parallel shafts. For each shaft there must be associatedbearings and other support parts associated therewith. The presentinvention advantageously eliminates one of the three shafts, in additionto the elimination of the chain and sprocket rpm reduction drive.

[0045] Transmission of power through a rotating shaft results in shaftwind-up. Shaft wind-up is essentially a lag in the power transmissionthrough the shaft. The amount of wind-up is dependent on the shaftmaterial as well as the shaft length. This lag in power transmissionintroduces inefficiencies and power loss into the drive train.Therefore, the elimination of the third shaft by use of a planetaryreduction drive provides a further significant advantage of reducingtotal wind-up in the system.

[0046] The elimination of the third shaft, along with elimination ofmany associated parts, results in a significant weight reduction in thedrive train. FIG. 11 is an exploded perspective view of the parts of theconventional prior art drive system of FIG. 10 that may be eliminated byone embodiment of the present invention, specifically the embodimentshown in FIG. 13. The reference numbers shown in FIG. 11 are listed inthe below table, with associated part numbers, quantity that can beeliminated by the FIG. 13 embodiment of the present invention, partdescription and weight in pounds. REF # PART in FIG. 11 NO. QTYDESCRIPTION WEIGHT 201 0702-375 1 DROPCASE W/STUDS 3.974 202 8011-143 1BOLT, CARRIAGE 0.038 203 8040-426 10 NUT, LOCK 0.112 204 8011-139 2BOLT, CARRIAGE 0.110 205 0123-523 4 BOLT, RIBBED 0.011 206 0607-025 9O-RING STUD 0.010 207 0623-117 2 BOLT, RIBBED 0.069 208 8050-247 6WASHER 0.012 209 0623-317 3 STUD 0.138 210 1602-051 1 BEARING, 1 IN 320211 1670-237 2 SEAL, O-RING 0.004 212 0670-163 1 O-RING, OIL LEVEL 0.001STICK 213 1602-087 1 SPROCKET 39T 2.036 214 1602-101 1 ADJUSTER, CHAIN0.066 215 0702-324 1 ARM, TIGHTENER-ASSY 0.496 216 1602-041 1 CHAIN, 70P1.635 217 8050-212 2 WASHER 0.002 218 0602-369 2 BUSHING, TIGHTENER0.004 ARM 219 0702-115 1 ARM, TIGHTENER 310 220 0623-122 2 NUT, LOCK0.021 221 0702-129 1 ROLLER, TIGHTENER 398 (INC 22) 222 0602-383 1BEARING, CHAIN .215 TIGHTENER 223 0123-082 2 PIN, COTTER — 224 1602-0521 BEARING, ⅞ IN 0.332 225 0602-198 2 PLATE, FLANGE 0.136 226 8041-426NUT, LOCK 0.021 227 0623-094 2 WASHER 0.002 228 0602-456 1 SPROCKET, 20T0.452 1 229 0602-437 1 SEAL, DROPCASE 0.021 230 0602-989 1 COVER,DROPCASE 1.985 231 8002-134 6 SCREW, CAP 0.186 232 8053-242 6 WASHER,LOCK 0.006 EXTERNAL TOOTH 233 0623-293 2 PLUG, DROPCASE 0.096 2340623-231 2 WASHER, SPRING 0.090 235 0623-465 2 NUT, LOCK 0.082 2360702-130 1 SPRING ASSEMBLY .090 237 0623-283 1 WASHER 0.008 238 0623-2841 WASHER 0.008 239 8050-217 2 WASHER 0.008 240 0123-641 2 WASHER, FIBER0.002 241 1602-152 1 COVER, OIL VENT 0.033 242 0623-081 4 SCREW,SELF-TAPPING 0.008 243 8050-242 1 WASHER 0.008 244 8042-426 1 NUT 0.016245 0602-462 1 STICK, OIL LEVEL 0.015 246 8002-135 1 SCREW, CAP 0.038247 8051-242 1 WASHER, LOCK 0.008 248 8011-137 1 BOLT, CARRIAGE 0.038249 0123-150 1 NUT 0.016 250 0616-964 1 GUARD, DROPCASE .520 2510602-876 1 ADAPTER, MANUAL 102 ADJUST 252 8050-252 AR WASHER 0.008 2530623-905 1 SEAL, MANUAL 008 ADJUST 254 8050-272 1 WASHER 0.008 2550702-266 1 SHAFT, DRIVEN 5.589 256 1602-099 1 BEARING, 1 IN (W/LOCK0.399 COLLAR) 257 0602-892 1 PLATE, FLANGE 0.136 258 8002-130 2 SCREW,CAP 0.044 TOTAL 20.492 LBS

[0047] While the above table is provided for purposes of demonstratingthe advantage of the current invention, it is important to keep in mindthat the exact parts utilized in the present invention will vary withinthe scope of the invention and should not be limited by this table. Usein the present invention, of one or more of the parts listed in thistable and shown in FIG. 11 does not bring a device outside the scope ofthe present invention.

[0048] Another Alternative Embodiment of the Present Invention:

[0049] A further embodiment of a drive train according to the principlesof the present invention is shown in FIGS. 12-15. FIG. 12 is aperspective view of an engine 301 and a drive train 303 according to theprinciples of the present invention. The drive train 303 includes oneembodiment of a continuously variable transmission, specifically, aprimary clutch 305 that is driven by the engine drive shaft (not shown),a drive belt 307 and a secondary clutch 308 driven by the drive belt307. The drive train 303 further includes a planetary gear system 300including drive shaft 310, track shaft 302, sprockets 304 and 306 andsecondary clutch 308 arranged along a center axis.

[0050]FIG. 14 is an exploded view of one embodiment of a planetary gearsystem 300 arranged along a center axis. FIG. 15 is a sectional view ofthe planetary gear system 300.

[0051] It is important to note that a planetary gear system according tothe present invention may be any gear reduction system that utilizes aplurality of planetary gears, a sun gear and a ring gear to realize anrpm reduction. A planetary gear system may utilize a stationary ringgear resulting in rotation of the cage holding the planetary gears.Alternatively, it is also within the scope of the present invention thatthe planetary gear system utilize a stationary cage resulting in arotating ring gear.

[0052] A planetary gear system of the present invention including theembodiment shown in FIG. 14 may be utilized either on the samelongitudinal axis of the engine drive shaft or the longitudinal axis ofthe secondary clutch. Each of these locations of a planetary gear systemis disclosed above. The embodiment of a planetary gear system 300 shownin FIGS. 12-15 may also be utilized in either of these locations. Forsake of brevity, the placement of the planetary gear system 300 is onlyshown and described in the position on the longitudinal axis of thetrack shaft. However, the invention certainly contemplates thepositioning of the planetary gear system 300 on the longitudinal axis ofthe engine drive shaft as would be well understood by one of skill inthe art when considered with the disclosure set forth above andthroughout this specification.

[0053] Turning first to the planetary gear system 300 shown in FIGS. 14and 15, the input shaft 310 (also referred to as a drive shaft or firstshaft) is coupled to and is driven by the secondary clutch 308 shown inFIG. 10. An input shaft is any shaft capable of transmitting rotationalenergy along its length. An input shaft can come in many differentconfigurations. One embodiment of an input shaft is input shaft 310. Theinput shaft 310 is integrally part of the sun gear 312. However, theinput shaft of this invention is not required to be integral with thesun gear. The input shaft 310 includes a larger diameter section 313that sealingly fits within a roller bearing 341 in the first housingmember 350. The seal between the input shaft 310 and the first housingmember is provided by a grease seal 315. The input shaft 310 isrotatably supported by one or more elements. One example of suchelements is a bearing or bushing. The embodiment shown in the figureshows the use of roller bearings, and more specifically, double row ballbearings 341 and 342.

[0054] A planetary gear system may include a planetary cage assembly. Aplanetary cage assembly is a plurality of planetary gears and a cage orother member that supports the plurality of planetary gears. Oneembodiment of a planetary cage assembly is planetary cage assembly 314.Planetary cage assembly 314 includes a cage including a pair ofplanetary gear plates 316 and 318 held together by spacer's 320 a-d. Theplates 316 and 318 carry a plurality of shafts 322, 324 326 and 328 thatrotatably support the planetary gears 330 a-d, respectively. The shafts322, 324, 326 and 328 may be integrally secured to the plates 316 and318, which in turn serve to maintain the planetary gears 330 a-d inspaced relationship around the sun gear 312. Spacer's 320 a-d may retainplates 316 and 318 in proper spaced relationship.

[0055] The planetary cage assembly 314 includes a weight bearingprotrusion 340 and a bearing or bushing positioned around theweight-bearing protrusion 340. One embodiment of the bearing is doublerow ball bearing 342. A weight bearing protrusion is a protrusion orother profile that is capable of structurally supporting the weight ofthe sun gear. The weight bearing protrusion 340, along with the doublerow ball bearing 342, are sized to fit within an opening 344 (see FIG.15) in the end of the integral member comprising the input shaft 310 andsun gear 312. The weight-bearing protrusion 340 therefore supports theweight of the sun gear 312 and input shaft 310.

[0056] A second shaft of a planetary gear system is any member coupledto one of the ring gear and planetary cage assembly wherein such memberis capable of acquiring at least a portion of the rotational energy ofthe one of the ring gear and planetary cage assembly that rotates. Asecond shaft may be integral with or connected to the planetary cageassembly or alternatively integral with or connected to the ring gear.One embodiment of a second shaft of a planetary gear system is secondshaft 346. Second shaft 346 is connected to plates 316 and 318 such thatrotation of the plates 316 and 318 results in rotation of the secondshaft 346. In the embodiment shown in FIG. 14, the second shaft 346 is amale-type splined member. It is certainly within the scope of thisinvention to have a second shaft having a female fitting or some otherstructure for connecting to whatever member the second shaft is driving.

[0057] Planetary gear system 300 further includes a housing 349,including first housing member 350 and a second housing member 352. Thehousing members 350 and 352 may be held together by suitable screws (notshown).

[0058] Double row ball bearing 360 provides bearing support of theplanetary cage assembly 314 by the second housing member 352.

[0059] A ring gear 354 is mounted in the second housing member 352. Thering gear 354 engages the planetary gears 330 a-d. As different sizering gears may be desired, the ring gear 354 may be removed from thesecond housing member 352 and replaced with a ring gear having adifferent diameter or different size gear teeth. The sun gear, planetarygears and the ring gear may be cast of high carbon steel.

[0060] The sun gear 312, planetary cage assembly 314 and ring gear 354are contained in housing 349, including first housing member 350 andsecond housing member 352. The housing 349 is sealed and containslubricating oil. The lubricating oil is anything that reduces the wearon the sun gear 312, planetary gears 330 a-d, and ring gear 354. In oneembodiment the oil used in the housing 349 is synthetic gear lube oralternatively synthetic transmission fluid.

[0061] In preferred embodiments of the planetary gear system of theinvention, the gear reduction ratio ranges from about 6:1 to 1:1. Thisis contrasted with the conventional chain and sprocket reduction ratiorange of from 1.6:1 to 2:1. The conventional chain and sprocket ratiorange is limited by the diameter of the sprockets and the strength ofthe smaller drive sprocket.

[0062] Now turning to one embodiment placement of the planetary gearsystem 300 within the drive train 303, we turn our attention to FIG. 13.FIG. 13 is a perspective view of a portion of the drive train 303 shownin FIG. 14. FIG. 13 includes some additional components not shown inFIG. 14, such as the right chassis 362, left chassis 368, and stiffener351. In the embodiment shown in FIG. 13, the planetary gear system 300is mounted coaxial with the track shaft 302. The input 310 is driven,through keyed connection, by the secondary clutch 308 of a continuouslyvariable transmission. The second or output shaft 346 of the planetarygear system 300 is coupled to and drives the track shaft 302. It iscertainly within the scope of this invention for the track shaft 302 andsecond shaft 346 to be an integral or one-piece member.

[0063] In the embodiment of the drive train of the present inventionshown in FIG. 13, the planetary gear system 300 is positioned adjacentto the outside of left chassis 362. It may be desirable to attach thehousing 349 to the left chassis 362 with bolts (not shown) through holesin the left chassis 362 such as holes 363 a-e. The planetary gear system300 is supported by a stiffener or bracket 351 that has one end attachedto the housing 349 of the planetary gear system 300 as shown, and theopposite end (not shown) secured to an engine mount (not shown).

[0064] The drive train of the present invention includes a track drivesprocket, alternatively referred to as a drive sprocket or simply as asprocket. A sprocket is any member attached to a track shaft and engagedwith a continuous drive track such that rotation of the track shaftcauses rotation of the sprocket that causes rotation of the continuousdrive track. The sprockets 304 and 306 are one well-known embodiment ofa sprocket.

[0065] A conventional brake caliper 364 and disk 366 are mounted on thetrack shaft 302 to the outside of the right chassis 368. Alternatively,the brake caliper and disk may be located to the inside of the rightchassis 368.

[0066] A bracket 370 containing a ring bearing (not shown) is secured tothe right chassis 368 and further supports the track shaft 302.

[0067] A continuously variable transmission is any mechanism or systemthat provides variable gear reduction. One embodiment of a continuouslyvariable transmission is referred to as a reduced rpm clutch oralternatively a clutch system. One embodiment of a continuously variabletransmission or clutch system is a primary clutch (alternativelyreferred to as a drive clutch), a belt and a secondary clutch(alternatively referred to as a driven clutch), wherein the secondaryclutch is driven by and connected to the primary clutch through thebelt. This type of continuously variable transmission is well known.

[0068] One embodiment of the present invention utilizes a secondaryclutch that has a smaller diameter than the prior art secondary clutch.Conventional secondary clutches typically have a diameter of about 10.5to 11.7 inches. One embodiment of the present invention utilizes asecondary clutch having a diameter between 8 inches and 9.5 inches. Theembodiment of the secondary clutch shown in FIGS. 12 and 13, namelysecondary clutch 308 has a diameter of 8.6 inches. This diameter ismeasured from the outer edge of sheaves 309 and 311.

[0069] Significant advantages result from the use of a smaller diametersecondary clutch. For example, the smaller diameter secondary clutchresults in less overall mass as well as less rotating mass. Furthermore,the smaller secondary clutch is more compact. Furthermore, as isdiscussed in more detail below, the smaller secondary clutch allows fora wider range of rpm reduction ratios.

[0070] The advantage of a more compact secondary clutch such assecondary clutch 308 is now further described. The present invention mayresult in placement of the secondary clutch on the same axis as thetrack shaft. A consequence of this placement is that a larger diameteror conventional secondary clutch is likely to strike the ground or snowin certain snowmobile driving circumstances. Therefore, a smallerdiameter secondary clutch has the advantage of being able to place suchclutch on the axis of the track shaft and yet maintain proper groundclearance. The only alternative to the smaller diameter secondary clutchwould be to raise the track shaft. However, a lower track shafttranslates into a desirable lower center of gravity for the snowmobile.It may also be desirable to configure the continuous track in aparticular path that requires the track shaft and sprockets to bepositioned in a lower position.

[0071] As mentioned above, a further advantage of the smaller diametersecondary clutch is the resulting wider range of rpm reduction ratios.The 8.6 inch diameter secondary clutch with a standard 8 inch diameterprimary clutch yields a start-up ratio (when the snowmobile is goingfrom being stationary to moving) of 2.77:1. The full ratio (when thesnowmobile is moving) is 2.04:1. This yields an overall ratio of thecontinuously variable transmission of 5.65:1. A conventionalcontinuously variable transmission with the larger 10.5 inch diametersecondary clutch and an 8 inch diameter primary clutch yields a start-upratio of 3.44:1 and a full ratio of between 1:1 and 1.21:1. Therefore,at best, the conventional overall ratio of the continuously variabletransmission is 4.16:1. This ratio change from 4.16:1 to 5.65:1 is a 36%increase in ratio range. The 36% increase in ratio range results in abetter ability for the snowmobile to take-off from starting position toa moving position with reduced jerkiness that is caused by the initialengagement of the transmission.

[0072] The operation of the embodiment drive train partially shown inFIGS. 12-15, including the continuously variable transmission is hereprovided. The engine 301 may be a conventional gasoline powered engineof the type generally found in snowmobiles. However, the engine may beany other type of engine suitable for driving a snowmobile. The enginedrive shaft (not shown in FIG. 12, but for example a shaft such as shaft15 in FIGS. 2 and 3) rotatably drives the primary clutch 305 that inturn drives the belt 307. The drive belt drives the secondary clutch 308that rotatably drives the input shaft 310. The sun gear 312 is thendriven by the input shaft 310. The sun gear 312 engages the planetarygears 330 a-d, which are rotatably supported, in the plates 316, 318.The force of the sun gear 312 acting on the planetary gears 330 a-dcause the gears 330 a-d to rotate and move along the ring gear 354thereby rotating the plates 316, 318. The rotation of plates 316, 318rotatably drives the second shaft 346. The second shaft 346 rotates atan rpm lower than the rotation of the input shaft 310 resulting in agear reduction. The second shaft 346 in turn drives sprockets 304 and306 that in turn engage and drive the endless track (such as endless orcontinuous track 14 of FIG. 1).

[0073] Another Embodiment—Forward/Reverse Planetary Unit:

[0074] The present invention may also include a forward/reverseplanetary unit, as shown in FIGS. 16-18, for driving the snowmobile inthe forward and reverse directions. Such a forward/reverse unit could beused in conjunction with any of the embodiments described above.

[0075] A forward/reverse planetary unit is a planetary drive system thatincludes the ability to operate in a reverse mode in which the secondshaft of the planetary drive system rotates in an opposite directionfrom the input shaft. FIGS. 16 and 17 are sectional views of oneembodiment forward/reverse planetary unit 400. FIG. 16 illustratesforward/reverse planetary unit 400 in forward mode in which the secondshaft 404 rotates in the same direction as the input shaft 402. FIG. 17illustrates the forward/reverse planetary unit 400 in reverse mode inwhich the second shaft 404 rotates in the opposite direction of theinput shaft 402.

[0076] First a discussion of the components of the forward/reverseplanetary unit 400 will be described. Then a discussion of the forwardand reverse modes will be provided in conjunction with FIGS. 16 and 17respectively.

[0077] A forward/reverse planetary unit includes an input shaft that isdriven either directly or indirectly by the engine drive shaft. An inputshaft may be integral or separate, but connected to, whatever drives it.For example, an input shaft may be integral with the engine drive shaft,or it may be a separate shaft. Furthermore, an input shaft could beintegral with a secondary clutch of a continuously variabletransmission. Alternatively, an input shaft could be integral with theoutput of an offset (offset is discussed below). What is meant by“integral” is that the two parts that are integral are in actuality onlyone piece or one member. Forward/reverse planetary unit 400 includesinput shaft 402.

[0078] A forward/reverse planetary unit also includes an output shaft.An output shaft either directly or indirectly drives the endless drivetrack of a snowmobile. An output shaft may be integral or separate, butconnected to, whatever it drives. For example, an output shaft may beintegral with a component of a continuously variable transmission in thesituation in which the forward/reverse planetary unit is on the frontend (drives the continuously variable transmission). Furthermore, anoutput shaft may be, but is not required to be, integral with the trackshaft. Forward/reverse planetary unit 400 includes output shaft 404.

[0079] An output shaft may, but is not required to, include a weightbearing protrusion. In the embodiment shown in FIGS. 16 and 17, theoutput shaft 404 includes a weight bearing protrusion 405.

[0080] Input shaft 402 includes a first sun gear 406 and a second sungear 408. Many different configurations and shapes and designs of sungears may be used in this invention. First and second sun gears 406 and408 are merely one embodiment.

[0081] A forward/reverse planetary unit includes a first planetaryassembly and a second planetary assembly. A planetary assembly includesa plurality of planetary gears and a cage to support the plurality ofplanetary gears.

[0082] Forward/reverse planetary unit 400 includes first planetaryassembly 410 that includes four planetary gears 412 (only two shown incross sectional views), and cage 414. In this embodiment, cage 414includes drum 416. Forward/reverse planetary unit 400 also includessecond planetary assembly 420 that includes four planetary gears 422(only two shown in cross sectional views), and cage 424. In thisembodiment, cage 424 is integral with ring gear 426. Cage 424 isconnected to the output shaft 404 so that rotation of the cage 424results in rotation of the output shaft 404. Ring gear 426 meshes withthe gear teeth on the planetary gears 412.

[0083] Forward/reverse planetary unit 400 also includes a second ringgear 430 that meshes with the gear teeth on planetary gears 422. In theembodiments shown in FIGS. 16 and 17, second ring gear 430 is supportedby a guide 431 in the housing 452.

[0084] A forward/reverse planetary unit includes a first locking deviceand a second locking device. The definition of a locking device forpurposes of this invention is any device or mechanism capable ofreleasably engaging either a cage or a ring gear to releasably preventthe cage or ring gear from rotating. A locking device may be a band orit may be some other mechanism. For example, a locking device may be anelectric magnet that can be turned on and off to create a magnetic fieldcapable of preventing rotational movement of a cage or ring gear.

[0085] The forward/reverse planetary unit 400 includes a first lockingdevice that is first band 440, and a second locking device that issecond band 442. First and second bands may be conventional reverselock-up bands used in the automobile industry. First and second bandsmay be made of a steel band with a friction material along the surfacethat contacts the braked member.

[0086] A means for actuating the first and second locking devices may beprovided. Means for actuating the first and second bands 440 and 442 mayinclude electric solenoids, mechanical means including levers, andhydraulic systems. Means 444 and 446 are shown in FIGS. 16 and 17, withmeans 444 positioned to actuate first band 440, and means 446 positionedto actuate second band 442. The means 444 and 446 may result in movementof plungers 448 and 450 respectively wherein the plungers interact withthe first and second bands 440 and 442 respectively. In the embodimentshown in FIGS. 16 and 17, forward/reverse planetary unit 400 includes ahousing 452 through which the plungers 448 and 450 extend. Housing 452may be sealed and contain lubricating oil such as discussed above withearlier embodiments.

[0087] Elements may be used to support the input shaft 402 and secondshaft 404 while still allowing the supported elements to rotate. Forexample, these elements may be bearings or bushings. In the embodimentshown in FIGS. 16 and 17, these elements are double row bearings 460,464 and 468.

[0088] A discussion of the forward/reverse planetary unit 400 in forwardmode is now provided in conjunction with FIG. 16. In forward mode,second ring gear 430 is prevented from any substantial rotation. This isaccomplished by actuating second band 442 to apply it to second ringgear 430. Furthermore, first band 440 is not actuated or applied to drum416. The result is that planetary gears 422 “walk” along stationarysecond ring gear 430. Therefore, cage 424 rotates in the same directionas input shaft 402, and hence second shaft 404 also rotates in the samedirection as input shaft 402.

[0089] A discussion of the forward/reverse planetary unit 400 in reversemode is now provided in conjunction with FIG. 17. In reverse mode firstband 440 is actuated to prevent any substantial rotational movement ofdrum 416 of cage 414. Second band 442 is not actuated or applied tosecond ring gear 430. The result is that planetary gears 412 drive ringgear 426 so that it rotates, and ring gear 426 is connected to thesecond shaft 404. Therefore, second shaft 404 rotates in reversedirection to input shaft 402.

[0090] It is noted that the gear reduction ratio of a forward/reverseplanetary unit in forward mode may be the same or it may be differentfrom the gear reduction ratio in reverse mode. The different ratios maybe adjusted by adjusting the number of gear teeth on the first andsecond sun gears 406 and 408 as well as appropriate changes to theplanetary and ring gears.

[0091] Further Embodiments—Offset:

[0092] Applicant also herein discloses an offset that may be used inconjunction with either a planetary gear system or with aforward/reverse planetary unit within a snowmobile. An offset is amechanism that transfers drive power from one axis to another. An offsetincludes a first offset member and a second offset member. The firstoffset member and the second offset member both are capable of rotatingin non-coaxial positions. An offset may include, but is not required toinclude, a gear reduction ratio. That is, the first and second offsetmembers may rotate at the same rotational speed or at differentrotational speeds.

[0093] First offset member includes gear teeth that are collectivelyreferred to as first offset gear. Likewise, second offset memberincludes gear teeth collectively referred to as second offset gear. Afirst offset gear is any form of gear capable of driving another gear. Asecond offset gear is a gear capable of being driven by a first offsetgear. The second offset member may be driven by direct contact betweenthe first offset gear and the second offset gear. Alternatively, theremay be an intermediate member or members such as a third member (notshown) including a third gear between the first and second offsetmembers.

[0094]FIG. 18 is a sectional view of one embodiment of an offsetcombined with a forward/reverse unit, namely offset and forward/reverseplanetary unit 500 (referred to hereinafter as unit 500). Unit 500includes first offset member 502 and second offset member 504. Firstoffset member 502 includes a shaft 506 with a first offset gear 508.

[0095] Elements may be used to support the first offset member whilestill allowing the first offset member to rotate. For example, theseelements may be bearings or bushings. In one embodiment, the firstoffset member 506 is rotationally supported by double row bearing 510,and single row bearing 514.

[0096] Second offset member 504 includes second offset gear 520 thatmeshes with first offset gear 508 of the first offset member 502. Secondoffset member 504 is rotatably supported by one or more elements. Forexample, these elements may be bearings or bushings. In one embodiment,the element supporting second offset member 504 may be single rowbearing 522.

[0097] Second offset member 504 is integral with input shaft 602 offorward/reverse planetary unit 600. Note that forward/reverse planetaryunit 600 is only shown in the Figures in reverse mode. However, forwardmode is also possible and is easily surmised from a review of FIG. 16.

[0098] Input shaft 602 includes a first sun gear 606 and a second sungear 608. Many different configurations and shapes and designs of sungears may be used in this invention. First and second sun gears 606 and608 are merely one embodiment.

[0099] A forward/reverse planetary unit includes a first planetaryassembly and a second planetary assembly. A planetary assembly includesa plurality of planetary gears and a cage to support the plurality ofplanetary gears.

[0100] Forward/reverse planetary unit 600 includes first planetaryassembly 610 that includes four planetary gears 612 (only two shown incross sectional views), and cage 614. In this embodiment, cage 614includes drum 616. Note that a cage, by definition is not required toinclude a drum. Rather, a cage with a drum is merely one embodiment of acage. Forward/reverse planetary unit 600 also includes second planetaryassembly 620 that includes four planetary gears 622 (only two shown incross sectional views), and cage 624. In this embodiment, cage 624 isintegral with ring gear 626. Cage 624 is connected to the output shaft604 so that rotation of the cage 624 results in rotation of the outputshaft 604. Ring gear 626 meshes with the gear teeth on the planetarygears 612.

[0101] Forward/reverse planetary unit 600 also includes a second ringgear 630 that meshes with the gear teeth on planetary gears 622. In theembodiment shown in FIG. 18, second ring gear 630 is supported by guide631 in housing 652.

[0102] A forward/reverse planetary unit includes a first locking deviceand a second locking device. The definition of a locking device forpurposes of this invention is any mechanism capable of releasablyengaging either a cage or a ring gear to releasably prevent the cage orring gear from rotating.

[0103] The forward/reverse planetary unit 600 includes a first lockingdevice that is first band 640, and a second locking device that issecond band 642. First and second bands may be conventional reverselock-up bands used in the automobile industry.

[0104] A means for actuating the first and second locking devices may beprovided. Means for actuating the first and second bands 640 and 642 mayinclude electric solenoids, mechanical means including levers, andhydraulic systems. Means 644 and 446 are shown in FIG. 18 with means 644positioned to actuate first band 640, and means 646 positioned toactuate second band 642. The means 644 and 646 may result in movement ofplungers 648 and 650 respectively wherein the plungers interact with thefirst and second bands 640 and 642 respectively. In the embodiment shownin FIG. 18, unit 500 includes a housing 652 through which the plungers648 and 650 extend. Housing 652 may be sealed and contain lubricatingoil as discussed above with earlier embodiments.

[0105] Elements may be used to support the second shaft 604 while stillallowing the second shaft 604 to rotate. For example, these elements maybe bearings or bushings. In one embodiment these elements are double rowbearings 652 and 654.

[0106] The unit 500 may be utilized in the drive train of a snowmobilein such a way that the first offset member is connected to the secondaryclutch of a continuously variable transmission which in turn is drivenby an engine drive shaft. For example, one could replace reduction drive19 in FIG. 3 with unit 500 of FIG. 18. In such a case the first offsetmember 506 would be connected to, or integral with, the secondary clutchand the second shaft 604 would be connected to, or integral with, thetrack shaft. The secondary clutch would drive the first offset member506 and the second shaft 604 would drive the endless drive track of thesnowmobile.

[0107] An offset combined with a planetary gear system is also disclosedhere. One embodiment offset and planetary gear system is shown insectional view in FIG. 19. Specifically, offset and planetary gearsystem 700 (hereinafter referred to as unit 700) is provided. Unit 700includes a first offset member 702 and a second offset member 704. Firstoffset gear 706 of first offset member meshes with second offset gear708 of second offset member 704 so that rotation of first offset membercauses rotation of second offset member. As with the offset discussedabove in relation to FIG. 18, there may be, but does not have to be, agear reduction ratio between the first offset member and the secondoffset member.

[0108] Elements may be used to support the first offset member whilestill allowing the first offset member to rotate. For example, theseelements may be bearings or bushings. In the embodiment of FIG. 19,first offset member 702 is rotationally supported by double row bearing710 and single row bearing 714.

[0109] Second offset member 704 is integral with input shaft 720 ofplanetary gear system 722 so that rotation of second offset member 704results in rotation of input shaft 720. Input shaft 720 includes sungear 724 that drives planetary gears 726 by being meshed with such.

[0110] Cage 730 is fixedly secured to housing 732 by clip 734 so thatcage 730 cannot rotate relative to housing 732. Ring gear 740 isintegral with second shaft 742 so that rotation of ring gear 740 causesrotation of second shaft 742. Ring gear 740 is driven by planetary gears726 by being meshed with such.

[0111] Unit 700 would be utilized in the drive train of a snowmobile inthe same location as unit 19 in FIGS. 2 and 3. That is, offset member702 is driven by the secondary clutch of a continuously variabletransmission, that is driven by an engine drive shaft. Output shaft 742drives an endless drive track, through for example a track shaft. Outputshaft 742 may be integral with the track shaft.

[0112] The above specification, examples and data provide a completedescription of the device and use of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

What is claimed is:
 1. A snowmobile comprising: a frame having a forwardportion and a rear portion, said frame including a pair of skissupporting said forward portion and an endless drive track supportingsaid rear portion, an engine supported in said frame, a drive trainconnected to said engine and to said endless drive track, said drivetrain including a planetary gear system, said planetary drive systemincluding a first shaft means and sun gear, said first shaft means beingdriven by said engine, planetary gears drivenly engaged with said sungear, and second shaft means including means engaged with said planetarygears, said second shaft means being driven by said planetary gears,said second shaft means driving said endless drive track.
 2. Thesnowmobile of claim 1 wherein said planetary gear system is driven bysaid engine engaging through a clutch system.
 3. The snowmobile of claim2 wherein said planetary gear system comprises four planetary gears andwherein said four planetary gears are equally spaced around said sungear.
 4. The snowmobile of claim 1 wherein said planetary gear systemincludes a plurality of planetary gears equally spaced around said sungear.
 5. The snowmobile of claim 4 wherein said planetary gear systemcomprises three planetary gears.
 6. The snowmobile of claim 4 whereinsaid second shaft means drives a differential and wherein saiddifferential drives said endless drive track.
 7. The snowmobile of claim6 wherein said first shaft means includes a first end adjacent saidengine and a second end adjacent said sun gear and wherein said firstshaft means is supported on a pair of ring bearings, the first of saidpair of ring bearings being disposed adjacent said first shaft end andthe second of said pair of ring bearings being disposed adjacent saidsecond end of said first shaft means.
 8. A snowmobile clutch systemcomprising: a planetary gear system, said planetary drive systemincluding a first shaft means including a sun gear, said first shaftmeans being adapted for driving engagement with a snowmobile engine,planetary gears drivenly engaged with said sun gear, and second shaftmeans including means engaged with said planetary gears, said secondshaft means being driven by said planetary gears; primary clutch meansin driven engagement with said second shaft means; secondary clutchmeans adapted for driving the track of a snowmobile; and belt meansinterconnecting said primary clutch means and said secondary clutchmeans.
 9. The snowmobile of claim 8 wherein said planetary gear systemcomprises four planetary gears and wherein said four planetary gears areequally spaced around said sun gear.
 10. The snowmobile of claim 9wherein said planetary gear system includes a plurality of planetarygears equally spaced around said sun gear.
 11. The snowmobile of claim10 wherein said planetary gear system comprises three planetary gears.12. A snowmobile comprising: a frame having a forward portion and a rearportion, said frame including a pair of skis supporting said forwardportion and an endless drive track supporting said rear portion, anengine supported in said frame, a drive train connected to said engineand to said endless drive track, said drive train including a reductiondrive comprising a planetary gear system, said planetary drive systemincluding a first shaft means and sun gear, said first shaft means beingdriven by said engine, planetary gears drivenly engaged with said sungear, and second shaft means including ring gear means engaged with saidplanetary gears, said second shaft means driving said endless drivetrack.
 13. The snowmobile of claim 12 wherein said planetary gear systemincludes a first shaft, said first shaft having a sun gear mounted atone and the opposite end of said first shaft being in driven engagementwith said engine, said planetary gear system further including a secondshaft, said second shaft having ring gear disposed at the first end ofsaid shaft, and a plurality of planetary gears disposed between said sungear and said ring gear, said planetary gears being driven by said sungear and said planetary gears serving to drive said ring gear.
 14. Thesnowmobile of claim 13 wherein said planetary gears are equally spacedaround said sun gear.
 15. The snowmobile of claim 14 wherein saidplanetary gears are supported in spaced relationship by ring platemeans.
 16. The snowmobile of claim 15 wherein said ring plate meanscomprise a pair of ring plates, one of said ring plates being disposedon each side of said planetary gears.
 17. The snowmobile of claim 16wherein said ring plate means further including a plurality of planetaryshafts, each of planetary shafts rotatably supporting one of saidplanetary gears.
 18. The snowmobile of claim 17 wherein said reductiondrive provides a reduction in the ratio of 1:3.
 19. The snowmobile ofclaim 17 wherein said first shaft includes a stub shaft extending beyondsaid sun gear and wherein said stub shaft is supported in a bearing. 20.The snowmobile of claim 19 wherein said second shaft is supported in abearing disposed adjacent said ring gear.
 21. A snowmobile including anengine with a drive shaft; a differential and a track; a planetary gearsystem interconnecting said engine drive shaft and said differential.22. The snowmobile of claim 21 wherein said planetary gear systemcomprises a sun gear, a plurality of planetary gears and a ring gear,wherein said planetary gears serve to provide driving power from saidsun gear to said ring gear.
 23. The snowmobile of claim 22 wherein saidsun gear is integrally mounted on the drive shaft of said engine. 24.The snowmobile of claim 23 wherein said planetary gears comprise fourplanetary gears.
 25. The snowmobile of claim 24 wherein said planetarygears comprise three planetary gears.
 26. The snowmobile of claim 25wherein said sun gear and engine drive shaft are rotatably supported inbearing means associated with said ring gear and drive shaft.
 27. Asnowmobile reduction gear system comprising a planetary gear system forinterconnecting a snowmobile engine drive shaft and a differential, saidplanetary gear system including a drive shaft and integral sun gear, aplurality of planetary gears disposed around said sun gear and a drivenshaft and integral ring gear, wherein said sun gear is adapted to bedriven by an planetary gears serve to provide driving power from saidsun gear to said ring gear.
 28. A snowmobile comprising: a frame havinga forward portion and a rear portion, said frame including a pair ofskis supporting said forward portion and an endless drive tracksupporting said rear portion, an engine supported in said frame, a drivetrain connected to said engine and to said endless drive track, saiddrive train including a primary clutch, a secondary clutch and aplanetary gear system, said primary clutch and said secondary clutchbeing interconnected by a belt, said planetary drive system including afirst shaft means and sun gear, said first shaft means being driven bysaid engine through said primary clutch, said belt, and said secondaryclutch, said planetary gears being drivenly engaged with said sun gear,and second shaft means including means engaged with said planetarygears, said second shaft means being driven by said planetary gears,said second shaft means driving said endless drive track.
 29. Thesnowmobile of claim 28 wherein said planetary gear system comprises fourplanetary gears and wherein said four planetary gears are equally spacedaround said sun gear.
 30. The snowmobile of claim 28 wherein saidplanetary gear system includes a plurality of planetary gears equallyspaced around said sun gear.
 31. The snowmobile of claim 30 wherein saidplanetary gear system comprises three planetary gears.
 32. Thesnowmobile of claim 33 wherein said second shaft means drives adifferential and wherein said differential drives said endless drivetrack.
 33. The snowmobile of claim 32 wherein said first shaft meansincludes a first end adjacent said engine and a second end adjacent saidsun gear and wherein said first shaft means is supported on a pair ofring bearings, the first of said pair of ring bearings being disposedadjacent said first shaft end and the second of said pair of ringbearings being disposed adjacent said second end of said first shaftmeans.
 34. A snowmobile comprising: a frame having a forward portion anda rear portion, said frame including a pair of skis supporting saidforward portion and an endless drive track supporting said rear portion,an engine supported in said frame, a drive train connected to saidengine and to said endless drive track, said drive train including aclutch system, said clutch system including a reduction drive comprisinga planetary gear system, said planetary drive system including a firstshaft means and sun gear, said first shaft means being directly drivenby said engine, planetary gears drivenly engaged with said sun gear, andsecond shaft means including ring gear means engaged with said planetarygears; primary clutch means driven by said second shaft means, secondaryclutch means and belt means providing driving engagement between saidprimary clutch means and said secondary clutch means, said secondaryclutch means serving to drive said endless track.
 35. A snowmobileincluding an engine with a drive shaft; a differential and a track; aclutch system including a planetary gear system interconnecting saidengine drive shaft and said differential.
 36. A snowmobile comprising: aframe having a forward portion and a rear portion, said frame includinga pair of skis supporting said forward portion and an endless drivetrack supporting said rear portion, an engine supported in said frame, adrive train connected to said engine and to said endless drive track,said drive train including a planetary gar system, primary clutch and asecondary clutch, said primary clutch and said secondary clutch beinginterconnected by a belt, said planetary drive system including a firstshaft means and sun gear, said first shaft means being driven by saidengine, said planetary gears being drivenly engaged with said sun gear,and second shaft means including means engaged with said planetarygears, said second shaft means being driven by said planetary gears,said second shaft means driving said endless drive track through saidprimary clutch and said secondary clutch.
 37. The snowmobile of claim 36wherein said second shaft means drives said primary clutch.
 38. Thesnowmobile of claim 37 wherein said first shaft means includes a firstend adjacent said engine and a second end adjacent said sun gear andwherein said first shaft means is supported on a pair of ring bearings,the first of said pair of ring bearings being disposed adjacent saidfirst shaft end and the second of said pair of ring bearings beingdisposed adjacent said second end of said first shaft means.
 39. Asnowmobile comprising: (a) a frame having a forward portion and a rearportion, said frame including a ski supporting said forward portion, andsaid frame including an endless drive track; (b) an engine supported insaid frame; (c) a drive train connected to said engine and to said drivetrack, wherein said drive train comprises: (i) an engine drive shaftcapable of being rotated by the engine, the engine drive shaft having afirst longitudinal axis; (ii) a track shaft having a second longitudinalaxis; (iii) a sprocket coupled to the track shaft wherein rotation ofthe track shaft causes rotation of the sprocket, and wherein thesprocket drives the endless drive track; (iv) a continuously variabletransmission connecting the engine drive shaft to the track shaftwherein the engine drive shaft drives the track shaft through thecontinuously variable transmission; and (v) a planetary gear systemhaving an input shaft and a second shaft, wherein the engine drive shaftdrives the input shaft and the second shaft drives the track shaft,wherein the input shaft and the second shaft are coaxial with one of theaxes selected from the group consisting of the first longitudinal axisand the second longitudinal axis, wherein there exists a gear reductionfrom the input shaft to the second shaft.
 40. The snowmobile accordingto claim 39 wherein the input shaft and the second shaft are coaxialwith the first longitudinal axis, and wherein the input shaft isconnected to and driven by the engine drive shaft, and wherein thesecond shaft is connected to and drives the continuously variabletransmission.
 41. The snowmobile according to claim 40, wherein theinput shaft and the engine drive shaft are a single integral shaft. 42.The snowmobile according to claim 39, wherein the input shaft and thesecond shaft are coaxial with the second longitudinal axis, and whereinthe input shaft is connected to and driven by the continuously variabletransmission, and wherein the second shaft is connected to and drivesthe track shaft.
 43. The snowmobile according to claim 42, wherein thesecond shaft and the track shaft are a single integral shaft.
 44. Thesnowmobile according to claim 39, wherein the gear reduction ratiocaused by the planetary gear system is between 1:1 and 6:1.
 45. Asnowmobile comprising: (a) a frame having a forward portion and a rearportion, said frame including a ski supporting said forward portion, andsaid frame including an endless drive track; (b) an engine supported insaid frame; and (c) a drive train connected to said engine and to saidendless drive track, wherein said drive train comprises: (i) a planetarygear system including a input shaft and a second shaft coaxial with theinput shaft, wherein the input shaft is driven by the engine and thesecond shaft is driven by the input shaft with a gear reduction from theinput shaft to the second shaft; and (ii) a sprocket that rotates aboutan axis, wherein the sprocket is coaxially connected to and driven bythe second shaft, and wherein the sprocket drives the endless drivetrack.
 46. The snowmobile according to claim 45, wherein the planetarygear system further comprises: (a) a sun gear connected to the inputshaft, wherein the sun gear defines an opening; (b) a ring gear whereinthe ring gear is rotationally stationary; and (c) a planetary cageassembly engaged with the sun gear and the ring gear, wherein theplanetary cage assembly comprises: (i) a weight bearing protrusionconnected to the second shaft, wherein the weight bearing protrusion isreceived by the opening in the sun gear, wherein the weight bearingprotrusion supports the sun gear; (ii) a cage connected to the secondshaft wherein rotation of the cage results in rotation of the secondshaft; and (iii) a plurality of planetary gears supported by the cage,wherein the planetary gears mesh with the sun gear and the ring gear,wherein rotation of the sun gear causes rotation of the planetary gears,and wherein rotation of the planetary gears within the ring gear causethe planetary cage assembly including the second shaft to rotate. 47.The snowmobile according to claim 45, wherein the drive train furthercomprises a continuously variable transmission, wherein the continuouslyvariable transmission is driven by the engine and wherein thecontinuously variable transmission drives the planetary gear system. 48.The snowmobile according to claim 47, wherein the continuously variabletransmission comprises a primary clutch, a belt, and a secondary clutch,wherein the primary clutch is driven by the engine, wherein thesecondary clutch is connected to the primary clutch by the belt, whereinthe secondary clutch is driven by the primary clutch, and wherein thesecondary clutch is coupled to and drives the planetary gear system. 49.A snowmobile comprising: (a) a frame having a forward portion and a rearportion, said frame including a pair of skis supporting said forwardportion, and said frame including an endless drive track; (b) an enginesupported in said frame; and (c) a drive train connected to said engineand to said endless drive track, said drive train consisting essentiallyof: (i) an engine drive shaft capable of being rotated by the engine,the engine drive shaft having a first longitudinal axis; (ii) a trackshaft having a second longitudinal axis; (iii) a sprocket coupled to thetrack shaft wherein rotation of the track shaft causes rotation of thesprocket, and wherein the sprocket drives the endless drive track; (iv)a continuously variable transmission connecting the engine drive shaftto the track shaft wherein the engine drive shaft drives the track shaftthrough the continuously variable transmission; and (v) a planetary gearsystem having an input shaft and a second shaft, wherein the enginedrive shaft drives the input shaft and the second shaft drives the trackshaft, wherein the input shaft and the second shaft are coaxial with oneof the axes selected from the group consisting of the first longitudinalaxis and the second longitudinal axis, wherein there exists a gearreduction from the input shaft to the second shaft.
 50. A planetary gearsystem for a snowmobile comprising: (a) an input shaft; (b) a sun gearconnected to the input shaft, wherein the sun gear defines an opening;(b) a ring gear wherein the ring gear is rotationally stationary; and(c) a planetary cage assembly engaged with the sun gear and the ringgear, wherein the planetary cage assembly comprises: (i) a cage member;(ii) a second shaft connected to the cage member, wherein rotation ofthe cage member causes rotation of the second shaft; (iii) a weightbearing protrusion connected to the cage and received by the opening inthe sun gear, wherein the weight bearing protrusion supports the sungear; and (iv) a plurality of planetary gears supported by the cagewherein the planetary gears mesh with the sun gear and the ring gear,wherein rotation of the sun gear causes rotation of the planetary gears,and wherein rotation of the planetary gears within the ring gear causethe planetary cage assembly including the second shaft to rotate. 51.The planetary gear system according to claim 50, wherein the pluralityof planetary gears comprises four planetary gears.
 52. The planetarygear system according to claim 50 further comprising a double row ballbearing connected to the weight bearing protrusion and received by theopening in the sun gear.
 53. The planetary gear system according toclaim 50, wherein the second shaft includes a distal end opposite fromthe connection to the weight bearing protrusion, wherein the distal endof the second shaft comprises a male splined end.
 54. The planetary gearsystem according to claim 50, wherein the second shaft includes a distalend opposite from the connection to the weight bearing protrusion,wherein the distal end of the second shaft comprises a female type end.55. The planetary gear system according to claim 50, further comprisinga housing including a first housing member and a second housing member,wherein the first housing member defines a first center opening thatreceives the second shaft, and wherein the second housing member definesa second center opening that receives the input shaft, and wherein thefirst housing member and second housing member are coupled together tocreate a sealed chamber between them, within which the planetary cageassembly and sun gear are at least in part positioned.
 56. Aforward/reverse planetary unit comprising: (a) an input shaft includinga first sun gear and a second sun gear adjacent the first sun gear; (b)a second shaft; (c) a first planetary assembly including a plurality offirst planetary gears and a first cage supporting the plurality of firstplanetary gears, wherein the plurality of first planetary gears isdriven by the first sun gear; (d) a second planetary assembly includinga plurality of second planetary gears and a second cage supporting theplurality of second planetary gears, wherein the plurality of secondplanetary gears are driven by the second sun gear; (e) a first ring gearconnected to the second shaft wherein rotation of the first ring gearcauses rotation of the second shaft, and wherein the first ring gear iscapable of being driven by the plurality of first planetary gears; (f) asecond ring gear wherein the second ring gear meshes with the pluralityof second planetary gears; (g) a first locking device engagable with thefirst cage, the first locking device having a released position and anapplied position, wherein the first locking device is disengaged fromthe first cage when in the released position and wherein the firstlocking device is engaged with the first cage preventing rotation of thefirst cage when in the applied position; and (h) a second locking deviceengagable with the second ring gear, the second locking device having areleased position and an applied position, wherein the second lockingdevice is disengaged from the second ring gear when in the releasedposition and wherein the second locking device is engaged with thesecond ring gear preventing rotation of the second ring gear when in theapplied position.
 57. The forward/reverse planetary unit of claim 56wherein the first locking device comprises a first band and wherein thesecond locking device comprises a second band.
 58. The forward/reverseplanetary unit of claim 57 further comprising first actuating means formoving the first band from the released position to the applied positionand second actuating means for moving the second band from the releasedposition to the applied position.
 59. A snowmobile comprising: (a) aframe having a forward portion and a rear portion, said frame includinga ski supporting said forward portion, and said frame including anendless drive track; (b) an engine supported in said frame; (c) a drivetrain connected to said engine and to said drive track, wherein saiddrive train comprises: (i) an engine drive shaft capable of beingrotated by the engine, the engine drive shaft having a firstlongitudinal axis; (ii) a track shaft having a second longitudinal axis;(iii) a sprocket coupled to the track shaft wherein rotation of thetrack shaft causes rotation of the sprocket, and wherein the sprocketdrives the endless drive track; (iv) a continuously variabletransmission connecting the engine drive shaft to the track shaftwherein the engine drive shaft drives the track shaft through thecontinuously variable transmission; and (v) a forward/reverse planetaryunit comprising: (A) an input shaft including a first sun gear and asecond sun gear adjacent the first sun gear, wherein the engine driveshaft drives the input shaft; (B) a second shaft coaxial with the inputshaft wherein the second shaft drives the track shaft, and wherein theinput shaft and the second shaft are coaxial with one of the axesselected from the group consisting of the first longitudinal axis andthe second longitudinal axis, wherein there exists a gear reduction fromthe input shaft to the second shaft; (C) a first planetary assemblyincluding a plurality of first planetary gears and a first cagesupporting the plurality of first planetary gears, wherein the pluralityof first planetary gears are driven by the first sun gear; (D) a secondplanetary assembly including a plurality of second planetary gears and asecond cage supporting the plurality of second planetary gears, whereinthe plurality of second planetary gears are driven by the second sungear; (E) a first ring gear connected to the second shaft whereinrotation of the first ring gear causes rotation of the second shaft, andwherein the first ring gear is capable of being driven by the pluralityof first planetary gears; (F) a second ring gear wherein the second ringgear meshes with the plurality of second planetary gears; (G) a firstlocking device engagable with the first cage, the first locking devicehaving a released position and an applied position, wherein the firstlocking device is disengaged from the first cage when in the releasedposition and wherein the first locking device is engaged with the firstcage preventing rotation of the first cage when in the applied position;and (H) a second locking device engagable with the second ring gear, thesecond locking device having a released position and an appliedposition, wherein the second locking device is disengaged from thesecond ring gear when in the released position and wherein the secondlocking device is engaged with the second ring gear preventing rotationof the second ring gear when in the applied position.
 60. The snowmobileaccording to claim 59, wherein the input shaft and the second shaft arecoaxial with the second longitudinal axis, and wherein the input shaftis connected to and driven by the continuously variable transmission,and wherein the second shaft is connected to and drives the track shaft.61. The snowmobile according to claim 60, wherein the second shaft andthe track shaft are a single integral shaft.
 62. The snowmobileaccording to claim 59 wherein the first locking device comprises a firstband, and wherein the second locking device comprises a second band. 63.A snowmobile comprising: (a) a frame having a forward portion and a rearportion, said frame including a ski supporting said forward portion, andsaid frame including an endless drive track; (b) an engine supported insaid frame; (c) a drive train connected to said engine and to said drivetrack, wherein said drive train comprises: (i) an engine drive shaftcapable of being rotated by the engine; (ii) a track shaft; (iii) asprocket coupled to the track shaft wherein rotation of the track shaftcauses rotation of the sprocket, and wherein the sprocket drives theendless drive track; (iv) a continuously variable transmission driven bythe engine drive shaft; (v) an offset comprising: (A) a first offsetmember connected to and driven by the continuously variabletransmission, the first offset member including a first offset gear; (B)a second offset member noncoaxial with the first offset member, whereinthe second offset member includes a second offset gear, wherein thesecond offset gear is driven by the first offset gear; and (vi) aforward/reverse planetary unit comprising: (A) an input shaft includinga first sun gear and a second sun gear adjacent the first sun gear,wherein the input shaft is driven by the second offset member; (B) asecond shaft coaxial with the input shaft wherein the second shaftdrives the track shaft; (C) a first planetary assembly including aplurality of first planetary gears and a first cage supporting theplurality of first planetary gears, wherein the first planetary gearsare driven by the first sun gear; (D) a second planetary assemblyincluding a plurality of second planetary gears and a second cagesupporting the plurality of second planetary gears, wherein the secondplanetary gears are driven by the second sun gear; (E) a first ring gearconnected to the second shaft wherein rotation of the first ring gearcauses rotation of the second shaft, and wherein the first ring gear iscapable of being driven by the plurality of first planetary gears; (F) asecond ring gear wherein the second ring gear meshes with the pluralityof second planetary gears; (G) a first locking device engagable with thefirst cage, the first locking device having a released position and anapplied position, wherein the first locking device is disengaged fromthe first cage when in the released position and wherein the firstlocking device is engaged with the first cage preventing rotation of thefirst cage when in the applied position; and (H) a second locking deviceengagable with the second ring gear, the second locking device having areleased position and an applied position, wherein the second lockingdevice is disengaged from the second ring gear when in the releasedposition and wherein the second locking device is engaged with thesecond ring gear preventing rotation of the second ring gear when in theapplied position.
 64. The snowmobile of claim 63 wherein the first cageincludes a drum, and wherein engagement of the first locking device withthe first cage comprises engagement of the first locking device with thedrum.
 65. The snowmobile of claim 63 wherein the second offset member isdirectly driven by the first offset member.
 66. The snowmobile of claim63 wherein the input shaft is integral with the second offset member.67. The snowmobile of claim 63 wherein the second shaft is integral withthe track shaft.
 68. The snowmobile of claim 63 wherein there is a gearreduction from the first offset member to the second offset member. 69.The snowmobile of claim 63 wherein the first locking device comprises afirst band, and wherein the second locking device comprises a secondband.
 70. A snowmobile comprising: (a) a frame having a forward portionand a rear portion, said frame including a ski supporting said forwardportion, and said frame including an endless drive track; (b) an enginesupported in said frame; and (c) a drive train connected to said engineand to said drive track, wherein said drive train comprises: (i) anengine drive shaft capable of being rotated by the engine; (ii) a trackshaft; (iii) a sprocket coupled to the track shaft wherein rotation ofthe track shaft causes rotation of the sprocket, and wherein thesprocket drives the endless drive track; (iv) a continuously variabletransmission driven by the engine drive shaft; (v) an offset comprising:(A) a first offset member connected to and driven by the continuouslyvariable transmission, the first offset member including a first offsetgear; and (B) a second offset member noncoaxial with the first offsetmember, wherein the second offset member includes a second offset gear,wherein the second offset gear is driven by the first offset gear; and(vi) a planetary gear system having an input shaft and a second shaft,wherein the second offset member drives the input shaft, and the secondshaft drives the track shaft, wherein there exists a gear reduction fromthe input shaft to the second shaft.
 71. The snowmobile of claim 70wherein the second offset member is directly driven by the first offsetmember.
 72. The snowmobile of claim 70 wherein the input shaft isintegral with the second offset member.
 73. The snowmobile of claim 70wherein the second shaft is integral with the track shaft.
 74. Thesnowmobile of claim 70 wherein there is a gear reduction from the firstoffset member to the second offset member.